#include <iostream>
#include <cmath>
#include <vector>


int main() {
    char current, last = 'x';
    int res = 0;
    bool found = false;
    while (std::cin >> current) {
        if (current == last) {
            if (found) {
                res++;
                found = false;
            }
            else {
                found = true;
            }
        }
        last = current;
    }

    if (found) res++;

    std::cout << res << std::endl;
    return 0;
}